Aircraft thermal management systems transfer heat from one component to another. Thermal management systems are provided on aircraft so that they can operate safely and efficiently by removing heat from thermally sensitive components, such as air streams, fuel and oil. Examples of thermal management systems include air-oil coolers and heat exchangers that reduce the temperature of compressor bleed air. To date, aircraft thermal management systems have generally been designed to transfer heat from a hot fluid stream directly to a heat sink. Heat exchangers used in these systems have been designed to run at the pressures needed by the hot fluid stream, leading to heat exchanger designs that are suboptimal with respect to efficiency, cooling capability and size. For example, some thermal management systems require transferring heat from a high-pressure fluid, such as fuel, to a low-pressure fluid, such as fan air. Heat exchanger designs in such a thermal management system needs to accommodate for the thermal and mechanical stresses caused by large pressure differentials. This typically requires the use of expensive, heavy materials at increased thicknesses to withstand the high pressure differentials and eliminate catastrophic failures. As a result, the efficiency of the heat transfer can be sub optimal due to the increased thickness of heat exchange surfaces.